In a conventional microfilm analog printer of the slit exposure type, a microfilm is illuminated and scanned by a film scan method or a lens scan method. With such an apparatus, generally, illumination has heretofore been provided by using a condenser lens system symmetric about an optical axis as an illuminating system.
An anamorphic flash device is known from Japanese Utility Model Publication Kokai No. 49-74241, for example. This device comprises a projector and a beam gun producing an effect comparable to a spot light source by combining an elongated flash tube and an anamorphic lens or a mirror with a spherical condenser lens.
With the condenser lens system symmetric about an optical axis in an ordinary illuminating optical system, illuminating light in a line or slit form is sufficient. However, the system is constructed to cause the light to illuminate areas transversely of the slit also. This results in some parts of the beam being wasted and the illuminating optical system itself being a large entity. Further, the device disclosed in the above Japanese publication has a light source limited to the elongated flash tube.
Such an illuminating optical system typically is used in a microfilm reader/printer. In view of this, a conventional microfilm reader/printer will now be described.
FIG. 16 is a sectional view of an optical system in a microfilm reader/printer of the film scan type as engaged in a printing operation. As shown, a microfilm 1005 is illuminated in a line form by illuminating light traveling thereto directly from a light source 1002 or after being reflected by a reflecting mirror 1001, through a condenser lens system 1004 which condenses the light. An image of microfilm 1005 illuminated in a line form is projected by a projecting lens system 1006 through a slit 1007 onto a photoreceptor drum 1008 rotating at velocity VI as indicated by an arrow, thereby forming a line image on the drum 1008. At this time, the microfilm 1005 is moved upward at velocity VO as indicated by an arrow. That is, the microfilm 1005 is moved at velocity VO which takes the rotating velocity VI of the photoreceptor drum 1008 and a projecting magnification ratio into account. The image is projected onto the photoreceptor drum 1008 with the slit 7 extending in the direction perpendicular to the sheet of drawings.
FIG. 17 is a sectional view of an optical system in a microfilm reader/printer of the lens scan type, in which a microfilm 1005 is held stationary. This optical system comprises a light source 1009 including a reflecting mirror, a condenser lens system 1010 and a projecting lens system 1006 arranged coaxially with one another are moved upward at velocity VL as indicated by an arrow for illuminating the microfilm 1005 linearly. An image of the illuminated microfilm 1005 is projected by the projecting lens system 1006 moving upward in synchronism with the light source 1009 and condenser lens system 1010, through a slit 1007 onto a photoreceptor drum 1008 rotating at velocity VI as indicated by an arrow, thereby forming an image on the drum 1008. In this case also, the moving velocity VL takes the rotating velocity VI of the photoreceptor drum 1008 and a projecting magnification ratio into account.